1. Field of the Invention
This invention relates to a coated glass article having a solar control coating. More particularly, this invention relates to a glass article having a multilayer coating and exhibiting high visible light transmittance with low total solar energy transmittance.
2. Summary of Related Art
Coatings on architectural glass are commonly utilized to provide specific energy absorption and light transmittance properties. Additionally, coatings provide desired reflective or spectral properties that are aesthetically pleasing. The coated articles are often used singularly or in combination with other coated articles to form a glazing or window unit.
Coated glass articles are typically produced “on-line” by continuously coating a glass substrate while it is being manufactured in a process known in the art as the “float glass process”. Additionally, coated glass articles are produced “off-line” through a sputtering process. The former process involves casting glass onto a molten tin bath which is suitably enclosed, thereafter transferring the glass, after it is sufficiently cooled, to lift out rolls which are aligned with the bath, and finally cooling the glass as it advances across the rolls, initially through a lehr and thereafter while exposed to the ambient atmosphere. A non-oxidizing atmosphere is maintained in the float portion of the process, while the glass is in contact with the molten tin bath, to prevent oxidation of tin. An oxidizing atmosphere is maintained in the lehr. In general, the coatings are applied onto the glass substrate in the float bath of the float bath process. However, coatings may also be applied onto the substrate in the lehr.
The attributes of the resulting coated glass substrate are dependent upon the specific coatings applied during the float glass process or an off-line sputtering process. The coating compositions and thicknesses impart energy absorption and light transmittance properties within the coated article while also affecting the spectral properties. Desired attributes may be obtainable by adjusting the compositions or thicknesses of the coating layer or layers. However, adjustments to enhance a specific property can adversely impact other transmittance or spectral properties of the coated glass article. Obtaining desired spectral properties is often difficult when trying to combine specific energy absorption and light transmittance properties in a coated glass article.
It would be advantageous to provide a coated glass article having a neutral tint that rejects solar energy in the summer and provides a low U value for the winter. A solar reducing glazing with a low emittance, and a low total solar energy transmittance, would significantly improve energy costs in buildings and homes while providing a desirable neutral tint.
It would also be advantageous to provide a solar reducing glazing that has a color neutral reflectance, a low emittance, a high visible light transmittance, and a low total solar energy transmittance. The use of such a neutral colored article in architectural glazings would permit the transmission of a high degree of visible light while rejecting a significant amount of near infrared energy. Furthermore, the low emittance characteristic of the glazing would minimize any indirect heat gain from absorption.